/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.flink.api.java.hadoop.mapred;

import org.apache.flink.api.common.io.FinalizeOnMaster;
import org.apache.flink.api.common.io.OutputFormat;
import org.apache.flink.api.java.hadoop.mapred.utils.HadoopUtils;
import org.apache.flink.api.java.hadoop.mapred.wrapper.HadoopDummyProgressable;
import org.apache.flink.api.java.hadoop.mapred.wrapper.HadoopDummyReporter;
import org.apache.flink.configuration.Configuration;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.mapred.FileOutputCommitter;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.JobContext;
import org.apache.hadoop.mapred.JobID;
import org.apache.hadoop.mapred.RecordWriter;
import org.apache.hadoop.mapred.TaskAttemptContext;
import org.apache.hadoop.mapred.TaskAttemptID;
import org.apache.hadoop.util.ReflectionUtils;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;


public abstract class HadoopOutputFormatBase<K, V, T> implements OutputFormat<T>, FinalizeOnMaster {

	private static final long serialVersionUID = 1L;

	private JobConf jobConf;
	private org.apache.hadoop.mapred.OutputFormat<K,V> mapredOutputFormat;
	protected transient RecordWriter<K,V> recordWriter;
	private transient FileOutputCommitter fileOutputCommitter;
	private transient TaskAttemptContext context;
	private transient JobContext jobContext;

	public HadoopOutputFormatBase(org.apache.hadoop.mapred.OutputFormat<K, V> mapredOutputFormat, JobConf job) {
		this.mapredOutputFormat = mapredOutputFormat;
		HadoopUtils.mergeHadoopConf(job);
		this.jobConf = job;
	}

	public JobConf getJobConf() {
		return jobConf;
	}

	// --------------------------------------------------------------------------------------------
	//  OutputFormat
	// --------------------------------------------------------------------------------------------

	@Override
	public void configure(Configuration parameters) {
		if(this.mapredOutputFormat instanceof Configurable){
			((Configurable)this.mapredOutputFormat).setConf(this.jobConf);
		}
	}

	/**
	 * create the temporary output file for hadoop RecordWriter.
	 * @param taskNumber The number of the parallel instance.
	 * @param numTasks The number of parallel tasks.
	 * @throws java.io.IOException
	 */
	@Override
	public void open(int taskNumber, int numTasks) throws IOException {
		if (Integer.toString(taskNumber + 1).length() > 6) {
			throw new IOException("Task id too large.");
		}

		TaskAttemptID taskAttemptID = TaskAttemptID.forName("attempt__0000_r_"
				+ String.format("%" + (6 - Integer.toString(taskNumber + 1).length()) + "s"," ").replace(" ", "0")
				+ Integer.toString(taskNumber + 1)
				+ "_0");

		this.jobConf.set("mapred.task.id", taskAttemptID.toString());
		this.jobConf.setInt("mapred.task.partition", taskNumber + 1);
		// for hadoop 2.2
		this.jobConf.set("mapreduce.task.attempt.id", taskAttemptID.toString());
		this.jobConf.setInt("mapreduce.task.partition", taskNumber + 1);

		try {
			this.context = HadoopUtils.instantiateTaskAttemptContext(this.jobConf, taskAttemptID);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}

		this.fileOutputCommitter = new FileOutputCommitter();

		try {
			this.jobContext = HadoopUtils.instantiateJobContext(this.jobConf, new JobID());
		} catch (Exception e) {
			throw new RuntimeException(e);
		}

		this.fileOutputCommitter.setupJob(jobContext);

		this.recordWriter = this.mapredOutputFormat.getRecordWriter(null, this.jobConf, Integer.toString(taskNumber + 1), new HadoopDummyProgressable());
	}

	/**
	 * commit the task by moving the output file out from the temporary directory.
	 * @throws java.io.IOException
	 */
	@Override
	public void close() throws IOException {
		this.recordWriter.close(new HadoopDummyReporter());
		
		if (this.fileOutputCommitter.needsTaskCommit(this.context)) {
			this.fileOutputCommitter.commitTask(this.context);
		}
	}
	
	@Override
	public void finalizeGlobal(int parallelism) throws IOException {

		try {
			JobContext jobContext = HadoopUtils.instantiateJobContext(this.jobConf, new JobID());
			FileOutputCommitter fileOutputCommitter = new FileOutputCommitter();
			
			// finalize HDFS output format
			fileOutputCommitter.commitJob(jobContext);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}
	
	// --------------------------------------------------------------------------------------------
	//  Custom serialization methods
	// --------------------------------------------------------------------------------------------
	
	private void writeObject(ObjectOutputStream out) throws IOException {
		out.writeUTF(mapredOutputFormat.getClass().getName());
		jobConf.write(out);
	}
	
	@SuppressWarnings("unchecked")
	private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
		String hadoopOutputFormatName = in.readUTF();
		if(jobConf == null) {
			jobConf = new JobConf();
		}
		jobConf.readFields(in);
		try {
			this.mapredOutputFormat = (org.apache.hadoop.mapred.OutputFormat<K,V>) Class.forName(hadoopOutputFormatName, true, Thread.currentThread().getContextClassLoader()).newInstance();
		} catch (Exception e) {
			throw new RuntimeException("Unable to instantiate the hadoop output format", e);
		}
		ReflectionUtils.setConf(mapredOutputFormat, jobConf);
	}
}
